linux-kernel - Re: [PATCH v2 2/3] leds: simatic-ipc-leds-gpio: split up into multiple drivers

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Message-ID: <20230302165824.4868f6da@md1za8fc.ad001.siemens.net>
Date:   Thu, 2 Mar 2023 16:58:24 +0100
From:   Henning Schild <henning.schild@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: Re: [PATCH v2 2/3] leds: simatic-ipc-leds-gpio: split up into
 multiple drivers

Am Thu, 2 Mar 2023 17:46:54 +0200
schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:

> On Thu, Mar 02, 2023 at 09:40:09AM +0100, Henning Schild wrote:
> > Am Wed, 1 Mar 2023 19:28:12 +0200
> > schrieb Andy Shevchenko <andriy.shevchenko@...ux.intel.com>:  
> > > On Wed, Mar 01, 2023 at 06:02:14PM +0100, Henning Schild wrote:  
> 
> ...
> 
> > > > +	.driver = {
> > > > +		.name = KBUILD_MODNAME,    
> > > 
> > > Strictly speaking this is an ABI (as something may instantiate the
> > > driver from the user space or elsewhere by this name. At the same
> > > time this may change with the file name change.
> > > 
> > > Personally I prefer explicit string literal here.  
> > 
> > Switching from one module to three the names have to change. People
> > who explicitly loaded the old module which supported multiple
> > machines, will now how to load either both oŕ know which one to
> > load.  
> 
> Wait, are you telling that now users load modules _manually_?!

No i am not, the modules all load automatically. I was trying to
construct a hypothetical case where the name change could affect users
doing unexpected things.

> > I personally think the ABI change is acceptable, the assumption
> > would be that the drivers load automatically anyhow. And since
> > there are no params i doubt users will have /etc/modprobe.d/ or
> > /sys/module/ stuff around.
> > 
> > And with the split i guess an ABI change can not be fully avoided.
> > Whether the names is explicit or implicit is another discussion and
> > just a matter of style. I prefer to stay with the currently used
> > pattern, it is not un-common in the kernel.  
> 
> The problem with that pattern is possible, while unlikely, renaming
> of the file which triggers this to be updated.
> 
> Under sysfs the folder will change its name. If user has a script
> relying on this, it will be broken. So, I prefer mine.

Yes, the name of the module will change ... and the location of module
metadata and params in sysfs, both not a big deal here. Because there
are no params, and there is not need to modprobe manually.

Henning

> > > > +	},    
>